FIGS. 1, 2A and 2B show a prior art vehicle suspension system in which one or more leaf springs 10 are coupled to an axle 12 with the leaf springs positioned below the axle. In general, configuring the suspension with the leaf springs 10 below the axle 12 provides a lower height suspension, which is desirable in some applications.
In this prior art construction, the axle 12 may have an upwardly projecting dowel or pin 14 that is inserted into an aperture of an upper axle retainer 16. An axle seat 18 is positioned between the leaf springs 10 and the axle 12. The axle seat 18 bears against the lower surface of the axle 12. As shown in FIG. 2A, the axle seat 18 may have an aperture 19 for receiving a dowel or pin 21 extending from the upper surface of the uppermost leaf spring of the leaf springs 10 to position the axle seat 18 relative to the leaf springs 10. The leaf springs 10 may be slidably or otherwise connected directly and/or indirectly (e.g., through shock absorbers as shown or otherwise coupled through other components) to a frame rail 24 of the vehicle.
A clamping element 20, which is generally aligned with the axle seat 18 and the upper axle retainer 16, may be provided and held in place by a pair of U-bolts 22, one being positioned on each side of the leaf springs 10. As a result, the leaf springs 10 and the axle 12 are held in place relative to each other by the combination of the upper axle retainer 16 with the pin 14 received in the aperture thereof, the axle seat 18, the pin 21, the clamping element 20 and the U-bolts 22 that secure this assembly together.
In other prior art configurations where the axle is positioned below the leaf springs, rather than above the leaf springs as shown in FIGS. 1, 2A and 2B, it is possible to weld the axle seat to the top surface of the axle. Due to stress concentrations that occur at the lower surface of the axle, however, welding the axle seat at this location can cause problems.
The prior art construction of FIGS. 1, 2A and 2B is satisfactory for vehicles operated on smooth surfaces, e.g., highways. After operation under severe conditions, however, such as on washboard roads or during off-road operation, the components of the suspension can wear and/or loosen. As a result, the assembly of the springs, axle seat, axle seat retainer and U-bolts can migrate or shift to some extent in the direction of the axle either inboard toward the frame rail or outboard away from the frame rail, which is undesirable.